Not Too Late to Optimize Potassium for Top Yields in 2011

Jan 06, 2011

PLYMOUTH, Minn. — With crop prices continuing to rise, growers will want to do all they can to maximize 2011 production. Fortunately, there is still time to plan for 2011 in order to take advantage of this income opportunity. Providing crops with adequate and balanced nutrition is key. Because recent soil test trends and research studies indicate soils in parts of North America may be lacking sufficient potassium (K), growers and their fertilizer dealers will want to pay particular attention to this key nutrient. Potassium is needed to ensure plants grow strong and healthy, from seedling to mature crop.

According to the International Plant Nutrition Institute (IPNI), soil test K levels across the continent are continuing to decrease, and as a result, the percentage of soil in negative balance for K continues to rise. The median K level for North America for the 2010 crop was 150 ppm, a 4 ppm decline from 2005. Median K levels in many states east of the Mississippi River and in the provinces of eastern Canada are at or below agronomic critical levels, indicating that 50 percent or more of the sampled areas represented likely require annual K application to avoid yield losses.

These soil test trends, coupled with environmental factors, suggest applying K fertilizer may be more important than ever for optimum crop yields. Fortunately, there is still time for growers to work with their fertilizer dealers to determine the right fertilizer mix to achieve peak plant growth and development for high yields.

“If soil samples were not taken this fall, soil tests can be completed as soon as soils thaw in the spring, then fertilizer dealers and growers can work together to determine the best source of potassium and application process for the crop and production system being used,” explains Dr. Dan Froehlich, agronomist with The Mosaic Company. “Keep in mind that the standard benchmark for potassium uptake for a 180-bushel corn yield is 240 pounds of potassium per acre. The critical level of potassium in the soil for optimum performance is approximately 165 ppm.” Research at Ohio State University shows that yields increased as soil test K increased above critical soil levels, and Froehlich adds that yields in this study increased as K increased to 200 ppm and 278 ppm, and nitrogen efficiency also was enhanced as soil K levels increased.

Impact of insufficient K

Because K plays an important role in plant development, insufficient levels of the nutrient can drastically alter the rest of the plant’s life cycle and greatly diminish the grain or forage quality. Potassium-deprived crops exhibit many symptoms of the deficiency, including:

Reduced nitrogen uptake

Poorly developed root systems

Reduced protein content

Susceptibility to water loss and wilting, and ultimately, reduced yield levels

Deficiency symptoms can be further heightened by agronomic and environmental conditions, which play a key role in the availability of nutrients for plant uptake. These factors make supplemental K even more important to optimize yields.

“Cool, wet years set up agronomic challenges for crops that exacerbate the impact of limited soil nutrients,” says Steve Phillips, Southeast U.S. region director with IPNI, a not-for-profit, science-based organization with a focus on agronomic education and research support.

Prolonged cool temperatures plus wet, compacted soils can cause irreparable damage to yield potential since more than 50 percent of the total K is taken up by corn plants in the first 50 days. Compaction and wet soils also may limit K uptake shortly before pollination, when corn plants remove more than 15 pounds of K2O per acre per day.

Agronomy resources for growers

The Mosaic Company offers a wealth of agronomy resources to growers, including the new 2011 Balanced Crop Nutrition Guide, on Back-to-Basics.net, a site dedicated to providing agronomy information to growers and the crop production industry. For more helpful production information, visit Back-to-Basics.net.